(a) Mention three main ways that food can be contaminated. (b) State five thickening agents for sauces.

(a) Three main ways that food can be contaminated

• Physical contamination, where foreign objects such as hair, glass, stones, insects or pieces of packaging fall into the food.
• Chemical contamination, where cleaning agents, pesticides, disinfectants or other chemicals come into contact with the food.
• Biological (bacterial) contamination, where harmful micro-organisms such as bacteria, moulds and viruses are transferred to food from people, pests, dirty equipment or other raw foods (cross-contamination).

(b) Five thickening agents for sauces

• Wheat flour (used in a roux or blended with liquid).
• Cornflour (corn starch).
• Arrowroot.
• Egg yolk (used to thicken and enrich, as in custard sauces).
• Beurre manié (equal parts of flour and butter kneaded together).

Other acceptable agents include ground rice, gelatine and a starch such as potato starch.